Worldwidely, misuse or abuse of antibiotics for treating bacterial infections has led to the rapid growth of mutant bacteria, thereby increasing interest in developing novel classes of antibiotics having excellent efficacy as alternatives to the existing drugs. Of them, daptomycin is a cyclic lipopeptide material produced as a secondary metabolite by a soil actinomycetes, streptomyces filamentosus, also called Streptomyces roseosporus. Daptomycin has a structure consisting of 13 amino acids and coupling of decanoyl side chain to the N-terminal tryptophan. At present, daptomycin is approved as a therapeutic agent for complicated skin and skin structure infections (cSSSI) of Gram-positive pathogens. Due to a peculiar structure of the cyclic lipopeptide antibiotic, daptomycin binds to the cell wall of Gram-positive bacteria to cause depolarization. Daptomycin is a fast acting agent having an excellent bactericidal activity, but depends on import in the whole quantity.
Generally, wild-type strains isolated from natural sources show low productivity and produce similar materials in complex, and therefore, they are not suitable for the production of desired antibiotics. Accordingly, there is a demand for a method capable of producing antibiotics in a high yield. It was reported that a streptomyces filamentosus strain with improved daptomycin productivity can be developed by ribosome engineering in order to increase daptomycin productivity (Biomed Res Int. 2013, 2013, Article ID 479742). However, this method is used to develop a strain of which daptomycin productivity is improved only by about 30%, compared to a parent strain thereof. Accordingly, a demand for a strain having remarkably improved daptomycin productivity still remains.